At least one of the preferred embodiments of the invention is disclosed as performing the function of preventing open access to a heated chamber wherein access to such heated chamber is to be denied until the temperature of the chamber has become reduced to a preselected temperature.
In the prior art where a chamber or other device is heated, it is often necessary to provide a lockout mechanism that will prevent access when the temperature of said chamber or other device is considered excessive in having a person become exposed to such temperature.
For example, many ovens intended for home cooking are equipped with a "cleaning cycle" mode of operation. When in such mode, the oven temperature is caused to be elevated to magnitudes at which grease or other carbon based deposits can readily ignite. Opening such an oven at the elevated cleaning temperatures could result in a sudden burst of flame from out of the oven with the attendant possibility of personal injury.
Similarly, other structural environments such as, for example, test chambers, fluid valves or other mechanisms may be of the type wherein they may be safely operated at or below a given or selected temperature, but not above such temperature. In other devices and/or apparatus the converse may be true; i.e., the devices and/or apparatuses can be operated above a certain temperature but not below. In situations such as these it is extremely desirable to have a lockout means that brings about latching or unlatching when the temperature at issue either goes above or below a desired control temperature. Further, it is desirable to have "fail safe" operation where the latching or unlatching action takes place without the need for external power.
A common solution to the foregoing by the prior art is to employ a bimetal leaf or bimetal coil responsive to a monitored temperature. In the prior art, the bimetal leaf or coil will bend or unbend as the monitored temperature is varied and such bending or unbending can be employed to, in turn, engage or disengage, for example, a latch or make, or break, a related electrical circuit.
In the prior art, bimetal disks are also used to provide a snap action when a particular transition temperature is passed. Among the difficulties experienced by the prior art, unit to unit (as in production quantities) variation in their operation results in the further need for calibration or significantly close and costly manufacturing dimensional tolerances. Further, experience has shown that in such prior art devices, the operating forces developed thereby are often of a low magnitude, even boardering on becoming an insufficient magnitude.
The invention as herein disclosed is primarily directed to the solution of the aforestated prior art problems as well as to other related and attendant problems.